[Matplotlib-users] autoscale when adding data to a Line2D?

I'm implementing a strip chart class by setting the data in a Line2D 
(well, one or more Line2D instances tied to one or more Subplots).

However, I find that when I do this I can't get the y axis to autoscale, 
even if I create the Line2Ds with animate=False.

Am I overlooking something really basic? If not, any suggestions?

Perhaps I should keep track of the y limits myself. That saves time when 
adding a new data point because I can compare it to cached limits 
(instead of scanning the whole data set). But it quickly gets messy if 
one handles nan correctly and matplotlib already does this so I was 
thinking matplotlib must have API code to help with this. But so far 
I've not figured it out from the docs (though matplotlib.ticker looks 
promising).

-- Russell